A great place to acquire all the materials is in Wintergrasp. Elementals that often drop the crystallized elements of all varieties can be found there. If your faction controls the fortress, Revenants that drop the crystallized materials more reliably also appear. Circling the area with Find Minerals on should eventually yield enough titanium ore.

The downside of searching in Wintergrasp is that if your faction is highly outnumbered, it can prove difficult to live long enough to mine these nodes.

Mining saronite in other areas where it's abundant like Icecrown or Scholazar basin will yield crystallized shadow and earth in abundance (most miners stack a lot of these over the time), leaving only the fire missing, which can be either farmed or purchased in AH, prices on your server will determine which one is more cost-effective.